JPH07303126A - Receiver - Google Patents

Abstract

PURPOSE:To compensate a DC offset of an orthogonal detection means by applying statistical processing to an output value of an orthogonal detection component in a timing when no reception signal is in existence so as to obtain a DC offset component. CONSTITUTION:An output of an orthogonal detection means in a timing when no reception signal is in existence is discriminated to be a DC offset and a noise component. A DC offset compensation timing control section 10 outputs a signal N in a timing when no reception signal is in existence. A DC offset compensation section 9 in this timing receives signals I, Q outputted from an orthogonal detection section 7 and implements statistic processing by receiving the signals for some number of times at points of time apart timewise to extract the DC offset component. The DC offset component when the reception signal is included in the signals I, Q received from the orthogonal detection section 7 is compensated by using the extracted DC offset.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication receiver, and more particularly, it enables compensation of a DC offset generated during quadrature detection.

[0002]

2. Description of the Related Art 16QAM (Quadrature Amplitude Mod), which has hitherto been difficult to put into practical use in land mobile communication
It has been demonstrated that the modulation method can be put to practical use by inserting a known signal into the transmission signal and using the fading distortion of the signal to compensate for the effect of the fading distortion of the unknown signal.

As shown in FIG. 2, a conventional radio communication receiver using the 16QAM system has a receiving antenna section 1 for detecting a radio frequency band signal from the air, and only a desired frequency band from the radio frequency band signal. A reception filter unit 2 for filtering the signal, a first-stage amplification unit 3 for amplifying a weak signal in the radio frequency band, a frequency conversion unit 4 for converting the received signal from the radio frequency band to the intermediate frequency band, and a signal in the intermediate frequency band. Variable gain amplifying section 5 for amplifying, and variable gain amplifying section 5
A gain control unit 6 for controlling a gain control signal based on the output of
A quadrature detector 7 that quadrature-detects the reception signal converted into the intermediate frequency band into I and Q signals that are baseband signals, and reproduces a carrier used for quadrature detection from the reception signal converted into the intermediate frequency band. A carrier reproducing section 8 for
A baseband signal processing unit 11 for digitally processing the I signal and the Q signal to reproduce the received data is provided.

Further, as shown in FIG. 3, the quadrature detection unit 7 receives inputs from the frequency conversion units 71 and 72 for converting the input intermediate frequency band received signal E into the base band signal band and the carrier reproduction unit 8. A phase conversion unit 73 that delays the phase of the reproduced carrier signal G by 90 degrees, and low-pass filter units 74 and 75 that remove signals other than the low frequency band from the frequency-converted signal.
And amplifiers 76 and 77 for amplifying signals, and A / D converters 78 and 79 for converting analog signals into digital signals.

In this receiving apparatus, first, the receiving antenna section 1 receives the radio frequency band signal A from the air and outputs it to the receiving filter 2. The reception filter unit 2 extracts a desired radio frequency band signal B from the radio frequency band signal A and outputs it to the first stage amplification unit 3. The first stage amplifier 3 amplifies the radio frequency band signal B and outputs it to the frequency converter 4. The frequency conversion unit 4 converts the amplified signal C in the radio frequency band into the signal D in the intermediate frequency band and outputs the signal D to the variable gain amplification unit 5. The variable gain amplifier 5 amplifies the input signal D while changing the amplification factor according to the gain control signal F, and outputs the amplified signal D to the next-stage circuit and the gain controller 6. The gain control section 6 outputs to the variable gain amplification section 5 a gain control signal F for controlling the variable gain amplifier so that the intermediate frequency band signal (IF signal) E is held at a constant value on a time average basis. The quadrature detection unit 7 performs quadrature detection of the IF signal E held at a constant value on a time average basis using the carrier signal G reproduced from the IF signal E by the carrier reproduction unit 8, and I of the baseband signal obtained. The signal H and the Q signal J are output to the baseband signal processing unit 11.

Inside the quadrature detector 7, the input IF signal E is input to the frequency converters 71 and 72. On the other hand, the reproduction carrier signal G is input to the 90-degree phase conversion unit 73, and the 90-degree phase conversion unit 73 delays the phase of the reproduction carrier signal G by 90 degrees and outputs it to the frequency conversion unit 72. The frequency conversion units 71 and 72 convert the input IF signal E into signals O and P based on the reproduction carrier G and the signal V obtained by delaying the phase of the reproduction carrier G by 90 degrees, respectively, and the low-pass filter units 74 and 75. Output to. The low-pass filter units 74 and 75 remove extra high frequency components from the input signals O and P, and amplify the baseband signals R and S.
And 77. The amplifiers 76 and 77 amplify the baseband signals R and S and output them to the A / D converters 78 and 79. The A / D converters 78 and 79 base the input baseband signals (analog). The band signals (digital) H and J are converted and output to the baseband signal processing unit 11.

The baseband signal processing unit 11 compensates the influence of the frequency offset and fading distortion contained in the I signal H and the Q signal J by digital signal processing, and outputs the received data K.

[0008]

However, in the conventional radio communication receiving apparatus, a DC offset (deviation) that causes fluctuations in the demodulation level in each of the low-pass filter section, the amplifying section, and the A / D converting section that constitute the quadrature detecting section. ) Is present, a DC offset component is generated in the I signal and the Q signal, which are received baseband signals, and the compensation performance of the frequency offset and fading distortion in the subsequent baseband signal processing unit is deteriorated. is there.

Fine adjustment is necessary to adjust the DC offset to zero, and in addition, this adjustment often shifts due to aging.

The present invention solves these conventional problems, and it is possible to compensate for the DC offset component generated in the quadrature detection section with a simple structure, thereby improving the compensation performance for frequency offset and fading distortion. It is an object of the present invention to provide a receiving device capable of suppressing deterioration.

[0011]

Therefore, according to the present invention, in a receiving apparatus including a quadrature detection means and a baseband signal processing means for performing frequency offset compensation or fading distortion compensation of a quadrature detected signal, A quadrature when a received signal exists based on the outputs of the DC offset compensation timing control means for outputting a signal representing the nonexistent timing and the quadrature detection means at the time when the signal is input from the DC offset compensation timing control means. A DC offset compensating means for compensating the DC offset component included in the output of the detecting means is provided, and the signal compensated by this DC offset compensating means is inputted to the baseband signal processing means.

The DC offset compensating means stores the output values of the quadrature detecting means at a plurality of points in time when signals are input from the DC offset compensating timing control means, and statistically processes the output values to obtain a DC offset component. It is configured to set a compensation amount for.

Further, the DC offset compensation timing control means is configured to output the signal at the time of the guard time assigned between the slots of the communication employing the TDM (time division multiplexing) system.

Further, the DC offset compensation timing control means is configured to output the signal in accordance with the "state in which the reception signal does not exist" forcibly created in the reception device.

[0015]

The output of the quadrature detection means at the timing when there is no received signal can be regarded as the DC offset component + noise component generated in the quadrature detection means. Therefore,
By statistically processing the output value of the quadrature detection means at this timing, the magnitude of the DC offset component generated in the quadrature detection means can be obtained. The DC offset compensating means compensates the DC offset in the presence of the received signal by adding a new DC offset component to the input signal so as to make the obtained DC offset component zero.

By compensating for the DC offset generated in the quadrature detection means, it is possible to avoid the deterioration of the compensation performance of the frequency offset and fading distortion performed in the baseband signal processing means, and it is possible to obtain high reception performance.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a receiving apparatus according to an embodiment of the present invention receives a DC offset compensating unit 9 for compensating for DC offset components of an I signal and a Q signal, and a signal from a transmitting side. A DC offset compensation timing control unit 10 for transmitting a non-existence (no reception signal exists) timing to the DC offset compensation unit 9. Other configurations are the same as those of the conventional device (FIGS. 2 and 3).

In this receiving apparatus, the receiving antenna unit 1 receives the radio frequency band signal A from the air, and the receiving filter unit 2
, A desired radio frequency band signal B is extracted from the radio frequency band signal A, the first stage amplifier 3 amplifies it, and the frequency converter 4 converts this signal C into an intermediate frequency band signal (IF signal) D. Then, the variable gain amplification unit 5 adjusts the gain of the IF signal while changing the amplification factor according to the gain control signal F input from the gain control unit 6, and the IF signal E held at a constant value on a time average basis. Is output to the quadrature detection unit 7. The quadrature detection unit 7 performs quadrature detection using the carrier signal G reproduced by the carrier reproduction unit 8 and outputs the I signal H of the baseband signal.
And a Q signal J are generated and output to the DC offset compensator 9.

In the DC offset compensating section 9, the detection block for detecting the DC offset amount is based on the DC offset compensating timing signal N input from the DC offset compensating timing control section 10 and at the timing when there is no received signal, the quadrature detecting section. The I signal H and the Q signal J output from 7 are taken in. The signal captured at this time can be regarded as the DC offset component + noise component generated in the quadrature detection unit 7. The detection block stores this signal, and at the time point of time separation, captures this signal several times and performs statistical processing to extract the DC offset component. The block for executing the DC offset compensation uses the extracted DC offset value to compensate the DC offset component when the I signal H and the Q signal J input from the quadrature detection unit 7 include the received signal. To do.

Specifically, this compensation is performed so that the DC offset component is minimized at the timing when the DC offset compensation timing control unit 10 outputs the DC offset compensation timing signal N (that is, the timing when there is no received signal). This can be performed by adding a new offset component and continuing this addition of the new offset component even when there is a received signal.

In TDM (time division multiplex) system communication for performing intermittent reception, the timing when there is no received signal is
The guard time assigned between slots is used. In addition, the receiving device forcibly creates a state in which there is no received signal, and D should be compensated based on the output of the quadrature detection unit 7 at that time.
The C offset component can also be obtained.

In this way, the I signal L and the Q signal M in which the DC offset component generated in the quadrature detection unit 7 is compensated are input to the baseband signal processing unit 11, and the baseband signal processing unit 11 converts these signals into these signals. The included frequency offset and fading distortion are compensated by digital signal processing, and received data N without distortion is output.

Since the DC offset compensation in the DC offset compensating unit 9 can be executed by digital signal processing, the DC offset compensating unit 9 and the baseband signal processing unit 11 are unified and the processing in each unit is performed. It is also possible to carry out integrally.

[0024]

As is apparent from the above description of the embodiments, the receiving apparatus of the present invention has the D generated in the quadrature detection section.
Since the C offset component can be compensated, the performance deterioration of the frequency offset compensation and the fading distortion compensation can be suppressed, and the reception quality can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a receiving device according to an embodiment of the present invention,

FIG. 2 is a block diagram showing a configuration of a conventional receiving device,

FIG. 3 is a block diagram showing a configuration of a quadrature detection unit of a conventional receiving device.

[Explanation of symbols]

 1 reception antenna section 2 reception filter section 3 first stage amplification section 4 frequency conversion section 5 variable gain amplification section 6 gain control section 7 quadrature detection section 8 carrier recovery section 9 DC offset compensation section 10 DC offset compensation section timing control section 11 baseband signal Processing unit 71 I signal frequency conversion unit 72 Q signal frequency conversion unit 73 90 degree phase conversion unit 74 I signal low pass filter unit 75 Q signal low pass filter unit 76 I signal amplification unit 77 Q signal amplification unit 78 I Signal A / D converter 79 Q signal A / D converter

Claims (4)

[Claims] 1. A receiving device comprising quadrature detection means and baseband signal processing means for performing frequency offset compensation and fading distortion compensation of the quadrature detected signal, and outputs a signal representing the timing at which the reception signal does not exist. The DC offset compensation timing control means for controlling the DC offset compensation timing control means, and the output of the quadrature detection means when the received signal is present, based on the output of the quadrature detection means at the time when the signal is input from the DC offset compensation timing control means. And a DC offset compensating means for compensating for a DC offset component, and the signal compensated by the DC offset compensating means is input to the baseband signal processing means. 2. The DC offset compensating means comprises the D
The output values of the quadrature detection means at a plurality of points in time when a signal is input from the C offset compensation timing control means are stored, and the output values are statistically processed to obtain the DC
The receiving apparatus according to claim 1, wherein a compensation amount for the offset component is set. 3. The reception according to claim 1, wherein the DC offset compensation timing control means outputs the signal at a time of a guard time assigned between slots of communication using the TDM method. apparatus. 4. The DC offset compensation timing control means outputs the signal according to a state in which a reception signal forcibly created in the reception device does not exist. The receiver described.